Recently, demand of nickel-cadmium battery (hereinafter, it is also referred to Ni-Cd battery) has remarkably increased as a superior battery accumulator. Life-time of such a Ni-Cd battery is about several years. Among the Ni-Cd batteries, Ni-Cd batteries for industrial use having relatively large size are broken into pieces and an anode electrode (Ni) and a cathode electrode (Cd) of the Ni-Cd batteries are separated from each other. Ni and Cd can be recovered by a wet method or a dry method.
On the other hand, Ni-Cd batteries for private use of a relatively small size are disposed by earth filling and so which the battery is installed in an equipment, or the battery is merely detached. Such a condition is not preferable because of environmental pollution and resource recycling. Particularly, it will become an important problem of recycling the Ni-Cd batteries having relatively small size in the future.
Japanese Patent Laid-open Publication No. 152138/1980 discloses a method for recycling Ni-Cd batteries wherein an outer shell portion of a used nickel-cadmium battery is partly opened in order to expose the battery body and then the nickel-cadmium battery is heat treated at 700.degree. to 1000.degree. C. in a non-oxidizing atmosphere in order to collect volatile cadmium.
Presently, batteries of size D (32 diameter.times.49 mm), naked batteries having the same size and a plurality of naked batteries (55.times.70.times.30 mm 135.times.65.times.20 mm) installed together in a resin case are used as Ni-Cd batteries for private use.
When the Ni-Cd batteries having the relatively small size are processed in order to collect cadmium according to the above described method, the opening has to be made in each battery. However, the Ni-Cd batteries have different shapes from each other. Therefore, one has to spend much time for a head-end process and it is difficult to utilize the above recovery method in a practical manner.
According to the above method, when cadmium is volatilized, impurities such as other components in a battery and material of an outer shell of the battery, particularly resin material of a resin packaging case, are recovered together with cadmium. Therefore, it is a problem that the purity of collected cadmium is reduced. If Fe is included in the collected cadmium as impurity and the cadmium is used as an anode electrode of a Ni-Cd battery, iron ions are produced during the charging cycle and the iron ions are transferred to the cathode electrode so that the capacity of the cathode electrode is reduced and self-discharge becomes large.
In addition, regarding as a used packaged battery, the battery is packaged in a stiff and shock resistant plastic resin case so that it is difficult to separate a battery body from the package.
Conventionally, there is a method for separating the battery body from the plastic case (package) by adding load on a packaged battery. However, in the method, it is very difficult to separate the battery body from the case without damaging the battery body, since the case is made of superior shock resistant plastic resin, for example, ABS resin, polycarbonate resin and so on.
Even if the packaged battery can be crushed and separated, there still exists a problem. It is the problem that cadmium is leaked from the battery and attached to the case. Additional cost is necessary to collect leaked and attached cadmium and clean the case.
As described above, in the conventional method for processing used packaged batteries, it is necessary to consider environmental pollution control systems for leaked material of an electrode caused by damaging an inside structure of the battery during mechanical processing.
A purpose of the present invention is to provide a method for separating a battery body from a resin case efficiently and processing the battery in order to recover high purity cadmium from a large number of used batteries having different sizes.